1. Field of the Invention
The present invention relates to a lens sheet adaptable to a transparent screen for a single light source projection television or the like using a liquid crystal, a digital light processor (hereinafter abbreviated to xe2x80x9ca DLPxe2x80x9d) or the like, and a producing method therefor.
2. Description of the Related Art
In recent years, a single light source projector of a matrix display using a liquid crystal, a DLP or the like has been found to be more excellent from the viewpoint of brightness, compactness or the like in comparison with a conventional CRT projector, and thus, it has been brought to the commercial stage. Since the matrix display is performed per pixel in the single light source projector, there may arise a problem of a moirxc3xa9 which is generated between a lens pitch of a lenticular lens included in a transparent screen for displaying an image and a pixel pitch of an image to be projected. In order to avoid the moirxc3xa9, the pitch of the lenticular lens need be as fine as about 0.2 mm or less.
It has been known that a light absorbing layer called as a black stripe or the like is effective as measure for reducing an adverse influence of outside light.
FIGS. 10A and 10B are cross-sectional views showing lenticular lens sheets in the prior art.
FIG. 10A is a view showing a conventional lenticular lens sheet in which a pitch is not made to be fine.
In the case where a light absorbing layer BS1 is formed in a conventional lenticular lens sheet 101 formed into a substantially elliptical shape in cross section, the light absorbing layer BS1 need be formed at a non-light collecting portion at which no retraction light L1 transmits.
FIG. 10B is a view showing the conventional lenticular lens sheet in which a pitch is made to be fine.
In the case where the pitch of the conventional lenticular lens sheet 101 is made to be fine (a pitch P1 is changed to a pitch P2), a focal distance becomes shorter since a unit lens is reduced in size. Consequently, the distance from the unit lens to the non-light collecting portion also becomes shorter, and therefore, a lenticular lens sheet 102 also need be reduced in thickness (a thickness t1 is changed to a thickness t2).
However, when the lenticular lens sheet becomes thinner according to the fineness of the pitch, as described above, there has arisen a problem of the difficulty of molding with high accuracy in producing by extrusion with high productivity, like in the prior art.
Furthermore, it is necessary to align the lenticular lens with the light absorbing layer with high accuracy, and thus, there have arisen problems of an increase in cost of a producing apparatus and deterioration of productivity.
In view of this, Japanese Patent Application Laid-open No. 10-111537 discloses a screen including an outside light absorbing layer in a lens unit of an elliptical lenticular lens as a lenticular lens of a fine pitch without any alignment. In this screen, it is unnecessary to dispose a light absorbing layer in a non-light collecting portion, thereby dispensing with alignment, with an advantage of fabrication of a lenticular lens of a fine pitch with relative ease.
However, since a light absorbing layer is disposed at a portion at which light transmits, there has arisen a problem of deterioration of light utilizing efficiency.
In the meantime, Japanese Patent Application Laid-open No. 2-22932 discloses a lenticular lens having an uneven shape in which the cross-sectional shape of a unit lens is not a substantially elliptical shape which is effective in collecting light and composed of a portion at which an incident light transmits, a portion at which the incident light is fully reflected and a light absorbing layer formed on the portion at which the incident light is fully reflected, and a producing method therefor.
In this screen producing method, a light absorbing layer is formed outside of a concave reflecting layer by a spraying, coating or squeezing method by the use of black ink. However, the use of these methods causes an uneven outward appearance such as coating thickness unevenness or drying unevenness, thereby arising a problem of the difficulty of the fabrication of a screen without any deficient outward appearance.
Moreover, since the methods for forming the reflecting layer and the light absorbing layer are independent of each other, there has arisen a problem of increases in cost of producing apparatuses and cost of fabrication.
An object of the present invention is to provide a highly accurate lens sheet of a fine pitch with high light utilizing efficiency, and a producing method capable of readily producing the lens sheet in reduced cost.
The above-described problems can be solved by providing a lens sheet as described below. Here, although for the sake of easy understanding, corresponding reference numerals are used for the explanation in preferred embodiments according to the present invention, they are not limited to those.
That is to say, a lens sheet (10 or 40) according to a first aspect of the present invention comprises: a lens layer (12) having a plurality of unit lenses, each of which is adapted to fully reflect a part of an incident light beam on a fully reflecting portion (12a) and then emit it from a light emitting portion (12b), arranged in a one- or two-dimensional direction on a light emitting side; and reflection attenuating layers (13 and 14) for reflecting the light beam incident from an incident light side and attenuating the light beam incident from the light emitting side, the reflection attenuating layers being formed of a material, which can form the layers via a vacuum film forming method, on the fully reflecting portion.
In the lens sheet (10 or 40) of the first aspect, a substrate film layer (11) may be disposed on the incident light side of the lens layer (12).
In the lens sheet (10 or 40), the reflection attenuating layers may be disposed on the fully reflecting portion (12a), and comprises a reflecting layer (13) for reflecting the light beam and a light attenuating layer (14 or 14-2) disposed nearer the light emitting side than the reflecting layer, for absorbing and/or scattering the light beam incident from the light emitting side, so as to attenuate the light beam.
In the lens sheet (10 or 40), the light attenuating layer (14) may be made of a metal oxide film.
In the lens sheet (10 or 40), a base metal mainly forming the metal oxide film for the light attenuating layer (14) may be the same as a material forming the reflecting layer (13).
In the lens sheet (10 or 40), the light attenuating layer (14-2) may be made of carbon.
In the lens sheet (10 or 40), the reflectance of the metal forming the reflecting layer (13) may be 85% or more in a visible region, and the spectral reflectance may be substantially flat.
In the lens sheet (10 or 40), the unit lens may be formed into a substantially trapezoidal shape in cross section, the oblique side of the trapezoid may serve as the fully reflecting portion (12a) and a portion corresponding to the upper base of the trapezoid may serve as the light emitting portion (12b).
In the lens sheet (40), a reinforcing plate (30) transparent to the light may be disposed nearer the light emitting side than the light emitting portion.
In the lens sheet (40), the reinforcing plate may contain a diffusing material for diffusing the light.
According to a second aspect or the present invention, a method for producing the lens sheet (10 or 40) comprises the steps of: (A) shaping the lens layer (12); (C and D) forming the reflection attenuating layers (13 and 14), by a vacuum film forming method, over the entire surface of the lens layer formed in the lens layer shaping process; and (E) removing the reflection attenuating layers formed on the light emitting portion in the reflection attenuating layer forming process, so as to expose the light emitting portion (12b).
In the method described above, the process of the step forming the reflection attenuating layers may comprise the steps of: (C) forming the reflecting layer (13) by a vacuum film forming method after the lens layer shaping process; and (D) forming the light attenuating layer (14) with a metal oxide film, on the reflecting layer formed in the reflecting layer forming process while introducing oxygen in a process similar to the process of the step forming the reflecting layer.
In the method described above, the process of the step shaping the lens layer on a substrate film (54) serving as the substrate film layer (11) may comprise the steps of: press-fitting the substrate film to a shaping die (51) in conformity with the shape of the lens layer via an ionizing radiation curable resin (53); irradiating the press-fitted substrate film with an ionizing radiation, so as to harden the ionizing radiation curable resin; and separating the substrate film from the shaping die, so as to remove the ionizing radiation curable resin hardened in the hardening process from the shaping die.
In the method described above, the process of the step (E) exposing the light emitting portion may comprise the steps of: sticking an adhesive film (76) onto the reflection attenuating layers (13 and 14) formed on the light emitting portion (12b); and peeling the adhesive film, so as to shift the reflection attenuating layers from the light emitting portion toward the adhesive film, thus removing the reflection attenuating layers.
The method described above may further comprise the step of: (B) forming a peeling layer (15) on the light emitting portion prior to the reflection attenuating layer forming processes (C and D).
In the method described above, the peeling layer (15) formed in the peeling layer forming process (B) may contain wax therein.
In the method described above, the processes (A to F) in the each step may be sequentially performed from one end of a lens sheet roll, from which a plurality of lens sheets are cut out.